

from tkinter import *


root = Tk()


ca = Canvas(root,

    width=400,
    height=300)

ca.pack()

def paint(event):
    x1,y1= (event.x-1),(event.y-1)
    x2,y2 = (event.x+1),(event.y+1)

    ca.create_oval(x1,y1,x2,y2,
    fill="blue")

ca.bind("<B1-Motion>",paint)





mainloop()
